1007.] 



PUBLIC DOCUMENT — No. 33. 



171 



to physiologists for many years; but the treatment of large 

 volumes of water with this chemical is, so far as we know, 

 comparatively recent. Those who wish to become familiar 

 with the more technical features of this subject are referred 

 to the older literature, much of which is in German, and to 

 the more recent publications of the United States Department 

 of Agriculture and our own State Board of Health. 



The treatment given during 1906 was similar to that of 

 1905, and consisted in applying 1 part of copper sulfate to 

 4,000,000 of water. The copper sulfate was placed in a 

 coarse bag attached to a canoe, which followed concentric 

 circles over the pond until the copper sulfate was all dissolved. 

 Samples of water were taken daily for bacterial examination 

 a few days before treatment and each day after until July 

 19, when the experiment was discontinued. The usual bac- 

 terial methods were employed, with the following results : — 



Table showing the Bcsults of treating the College Pond ivith Co'piJer 

 Sulfate at the Rate of 1 Part of Coi^per Sulfate to 4,000,000 

 of Water. {Treated June 14, 1906.) 



[Number of bacteria per c. c. of water.] 



June 10 7, 



11 6, 



12 5, 



13, 7, 



14, 7; 



14 



14 



15, 



16 



17, 



18, 



19, 



20 



21, 1, 



22 1, 



23, 



24 , . 



25 



0051 

 0341 

 7571 

 1881 

 ,1581 

 1302 

 56 3 

 1424 

 156 

 156 

 341 

 554 

 769 

 ,000 

 000 

 756 

 768 

 927 



June 26, 



27, 

 28, 

 29, 

 30, 

 July 1, 

 2> 

 3, 

 4, 



9, 



n, 



13, 



15, 

 17, 

 19, 



846 

 1,085 

 1,231 

 1,265 

 1,006 

 1,365 

 1,231 

 1,308 

 1,231 

 1,006 

 1,084 

 1,000 

 1,208 

 1,208 

 1,275 

 1,462 

 1,770 



1 Before treatment. 



- One hour after treatment. 



3 Two hours after treatment. 



■< Twenty -four hours after treatment. 



